# List of common physics notations

This is a list of common physical constants and variables, and their notations. Note that bold text indicates that the quantity is a vector.

## Latin characters

Symbol Meaning SI unit of measure
${\displaystyle \mathbf {A} }$  magnetic vector potential tesla meter (T⋅m)
${\displaystyle A}$  area square meters (m2)
amplitude meter
atomic mass number unitless
${\displaystyle \mathbf {a} }$  acceleration meters per second squared (m/s2)
${\displaystyle \mathbf {B} }$  magnetic flux density
also called the magnetic field density or magnetic induction
tesla (T), or equivalently,
weber per square meter (Wb/m2)
${\displaystyle C}$  capacitance farad (F)
heat capacity joule per kelvin (J⋅K−1)
constant of integration varied depending on context
${\displaystyle c}$  speed of light (in vacuum) 299,792,458 meter per second (m/s)
speed of sound 340.29 meter per second (m/s)
specific heat capacity joule per kilogram per kelvin (J⋅kg−1⋅K−1)
viscous damping coefficient kilogram per second (kg/s)
${\displaystyle \mathbf {D} }$  electric displacement field
also called the electric flux density
coulomb per square meter (C/m2)
${\displaystyle D}$  density kilograms per cubic meter (kg/m3)
${\displaystyle d}$  distance meter (m)
direction unitless
impact parameter meter (m)
diameter meter (m)
differential (e.g. ${\displaystyle dx}$ ) varied depending on context
${\displaystyle d\mathbf {A} }$  differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S square meter (m2)
${\displaystyle dV}$  differential element of volume V enclosed by surface S cubic meter (m3)
${\displaystyle \mathbf {E} }$  electric field newton per coulomb (N⋅C−1), or equivalently, volt per meter (V⋅m−1)
${\displaystyle E}$  energy joule (J)
Young's Modulus pascal (Pa) or newton per square meter (N/m2)
${\displaystyle e}$  eccentricity unitless
2.71828... (base of the natural logarithm) unitless
electron unitless
elementary charge coulomb (C)
${\displaystyle \mathbf {F} }$  force newton (N)
${\displaystyle F}$  Faraday constant coulombs per mole (C⋅mol−1)
${\displaystyle f}$  frequency hertz (Hz)
function
friction newton (N)
${\displaystyle G}$  electrical conductance siemens (S)
gravitational constant newton meter squared per kilogram squared (N⋅m2/kg2)
${\displaystyle g}$  acceleration due to gravity meters per second squared (m/s2), or equivalently, newtons per kilogram (N/kg)
${\displaystyle \mathbf {H} }$  magnetic field strength ampere per meter (A/m)
${\displaystyle H}$  Hamiltonian joule (J)
${\displaystyle h}$  height meter (m)
Planck constant joule second (J⋅s)
${\displaystyle \hbar }$  reduced Planck constant joule second (J⋅s)
${\displaystyle I}$  action joule second (J⋅s)
intensity watt per square meter (W/m2)
sound intensity watt per square meter (W/m2)
electrical/conventional current ampere (A)
moment of inertia kilogram meter squared (kg⋅m2)
${\displaystyle i}$  intensity watt per square meter (W/m2)
imaginary unit unitless
${\displaystyle \mathbf {\hat {i}} }$  Cartesian x-axis basis unit vector unitless
${\displaystyle \mathbf {J} }$  current density ampere per square meter (A/m2)
impulse kilogram meter per second (kg⋅m/s)
${\displaystyle \mathbf {j} }$  jerk meters per second cubed (m/s3)
${\displaystyle j}$  imaginary unit (electrical) unitless
${\displaystyle \mathbf {\hat {j}} }$  Cartesian y-axis basis unit vector unitless
${\displaystyle K}$  kinetic energy joule (J)
${\displaystyle k}$  Boltzmann constant joule per kelvin (J/K)
wavenumber, wave vector radians per meter (m−1)
stiffness newtons per meter (N⋅m−1)
${\displaystyle \mathbf {\hat {k}} }$  Cartesian z-axis basis unit vector unitless
${\displaystyle L}$  inductance henry (H)
luminosity watt (W)
angular momentum newton meter second (N⋅m⋅s or kg⋅m2⋅s−1)
Lagrangian joule (J)
${\displaystyle l}$  length meter (m)
azimuthal quantum number unitless
${\displaystyle M}$  magnetization amperes per meter (A/m)
moment of force
often simply called moment or torque
newton meter (N⋅m)
${\displaystyle m}$  mass kilogram (kg)
${\displaystyle N}$  normal vector unit varies depending on context
atomic number unitless
${\displaystyle n}$  refractive index unitless
principal quantum number unitless
amount of substance mole
${\displaystyle P}$  power watt (W)
probability unitless
${\displaystyle \mathbf {p} }$  momentum kilogram meter per second (kg⋅m/s)
${\displaystyle p}$  pressure pascal (Pa)
${\displaystyle Q}$  electric charge coulomb (C)
Heat joule (J)
${\displaystyle q}$  electric charge coulomb (C)
${\displaystyle R}$  electrical resistance ohm (Ω)
Ricci tensor reciprocal square meter (m−2)
gas constant joule per mole per kelvin (J⋅mol−1⋅K−1)
${\displaystyle \mathbf {r} }$  radius vector (position) meter (m)
${\displaystyle r}$  radius or distance meter (m)
${\displaystyle S}$  surface area m2
entropy joule per kelvin (J/K)
action joule second (J⋅s)
${\displaystyle \mathbf {s} }$  displacement meter (m)
${\displaystyle s}$  arc length meter (m)
${\displaystyle T}$  period second (s)
temperature kelvin (K) or Celsius (C)
${\displaystyle t}$  time second (s)
${\displaystyle \mathbf {U} }$  four-velocity meter per second (m/s)
${\displaystyle U}$  potential energy joule (J)
internal energy joule (J)
${\displaystyle u}$  relativistic mass kilogram (kg)
energy density joule per cubic meter (J/m3) or joule per kilogram (J/kg) depending on the context
${\displaystyle V}$  voltage
also called electric potential difference
volt (V)
volume cubic meter (m3)
shear force
${\displaystyle \mathbf {v} }$  velocity meter per second (m/s)
${\displaystyle W}$  weight newton (N)
mechanical work joule (J)
${\displaystyle w}$  width meter (m)
${\displaystyle \mathbf {x} }$  position vector meter (m)
displacement meter (m)
${\displaystyle x}$  a generic unknown varied depending on context
${\displaystyle Z}$  electrical impedance ohm (Ω)

## Greek characters

Symbol Name Meaning SI unit of measure
${\displaystyle \alpha }$  alpha alpha particle
fine-structure constant unitless
${\displaystyle \beta }$  beta velocity in terms of the speed of light c unitless
beta particle
${\displaystyle \gamma }$  gamma Lorentz factor unitless
photon
gamma ray
shear strain
heat capacity ratio unitless
${\displaystyle \Delta }$  delta change in a variable (e.g. ${\displaystyle \Delta x}$ ) unitless
Laplace operator per square meter (m−2)
${\displaystyle \delta }$  displacement (usually small) meter (m)
Dirac delta function
${\displaystyle \epsilon }$  epsilon permittivity farad per meter (F/m)
strain unitless
${\displaystyle \varepsilon _{0}}$  epsilon nought vacuum permittivity constant farad per meter (F/m)
${\displaystyle \zeta }$  zeta damping ratio unitless
${\displaystyle \eta }$  eta energy efficiency unitless
(dynamic) viscosity (also ${\displaystyle \mu }$ ) pascal second (Pa⋅s)
jerk meter per second cubed (m/s3)
${\displaystyle \theta }$  theta angular displacement radian (rad)
${\displaystyle \mathrm {K} }$  kappa torsion coefficient
also called torsion constant
${\displaystyle \Lambda }$  lambda cosmological constant per second squared (s−2)
${\displaystyle \lambda }$  wavelength meter (m)
linear charge density coulomb per meter (C/m)
eigenvalue non-zero vector
${\displaystyle \mathbf {\mu } }$  mu magnetic moment ampere square meter (A⋅m2)
coefficient of friction unitless
(dynamic) viscosity (also ${\displaystyle \eta }$ ) pascal second (Pa⋅s)
permeability (electromagnetism) henry per meter (H/m)
reduced mass kilogram (kg)
gravitational parameter
${\displaystyle \mathbf {\mu } _{0}}$  mu nought vacuum permeability constant or magnetic constant henry per meter (H/m)
${\displaystyle \nu }$  nu frequency hertz (Hz)
kinematic viscosity meters squared per second (m2/s)
neutrino
${\displaystyle \pi }$  pi 3.14159... (irrational number) unitless
${\displaystyle \rho }$  rho mass density
usually simply called density
kilogram per cubic meter (kg/m3)
volume charge density coulomb per cubic meter (C/m3)
resistivity ohm meter (Ω⋅m)
${\displaystyle \Sigma }$  sigma summation operator
${\displaystyle \sigma }$  sigma area charge density coulomb per square meter (C/m2)
electrical conductivity siemens per meter (S/m)
normal stress pascal (Pa)
scattering cross section barn (10^-28 m^2)
${\displaystyle \tau }$  tau torque newton meter (N⋅m)
shear stress pascal (Pa)
time constant second (s)
6.28318... () unitless
${\displaystyle \Phi }$  phi field strength unit varies depending on context
magnetic flux weber (Wb)
${\displaystyle \phi }$  electric potential volt (V)
Higgs field work function
${\displaystyle \Psi }$  psi wave function m−3/2
${\displaystyle \Omega }$  omega electric resistance ohm
${\displaystyle \omega }$  angular frequency radian per second (rad/s)

## Other characters

Symbol Name Meaning SI unit of measure
${\displaystyle \nabla \cdot }$  nabla dot the divergence operator
often pronounced "del dot"
per meter (m−1)
operator${\displaystyle \nabla \times }$  nabla cross the curl operator
often pronounced "del cross"
per meter (m−1)
area${\displaystyle \nabla }$  nabla delta (differential operator)
${\displaystyle \partial }$  "der", "dow", "die", "partial" or simply "d" partial derivative (e.g. ${\displaystyle \partial y/\partial x}$ )
${\displaystyle \Box }$  D'Alembert operator ${\displaystyle \nabla ^{2}-\partial _{t}^{2}}$
${\displaystyle \langle \,\,\rangle }$  angle brackets average

sometimes over Maxwell–Boltzmann distribution

${\displaystyle \langle \ |\ \rangle }$  Dirac notation